Known processes for fabricating castable composite parts are very complicated and expensive. A large portion of the complexity and expense is associated with manufacturing related molds.
Typically, the first step in producing a castable composite part is to acquire a prototype that embodies the desired features; the prototype is given to a tool and die facility that makes molds for replicating the prototype. The prototype part may encompass an assembly of individual components, in which case a series of individual molds are required. In some cases, the mold is manufactured directly from a set of drawings in a three dimensional computer readable format which embody the desired features. A mold, a set of molds or set of pieces to make a mold is often referred to as “tooling.”
Often times, castable composite parts are made with resins which require a thermal curing operation subsequent to being injected into the mold in a liquid state and prior to being removed therefrom in a solid state. Therefore, molds for producing castable composite parts are typically made of metal, usually a type of steel or aluminum with an associated melting temperature above the anticipated curing temperature of the associated resin. Machining methods associated with producing metal molds are very expensive. Typically, a mold for casting a part with high surface definition and intricate three dimensional detail is the most complex and expensive.
Processes for manufacturing castable composite parts typically employ a plurality of molds. The individual molds are assembled, the resin is injected, the mold with resin is subjected to heat, the cured part is removed and the mold is recycled to produce another part. It is common to coat the interior portions of the mold with a “mold release agent” prior to injecting the resin. The mold release agent assists in removal of the cured part from the mold. In the case of a complex part and a mold with many pieces, the processes associated with handling the mold are costly.
The high initial cost associated with making metal molds requires high production of the associated composite part to make the overall process cost effective. High cost is compounded with regard to complex parts in that the processing costs are escalated as well. With known molding technology, subsequent changes in the part and single part production are expensive and, oftentimes, uneconomical and unfeasible.
Metal molds limit the complexity of the associated part which can be produced. Since the resin is injected into the mold as a liquid and then is cured within the mold to form a solid composite part, metal molds used to cast complex parts must be adequately separable such that the cured part can be removed without damage. Complex parts with high surface definition and three-dimensional shape variations require molds which are comprised of multiple pieces; the individual mold pieces are designed to separate relative to the castable composite part shape.
Additionally, metal molds are not transparent, therefore, classes of resins which are cured using ultra-violet (UV), visible (VIS), near infrared (NIR) or infrared (IR) light are not compatible. Use of UV and IR light for curing is preferred in many cases. Inherently, visual inspection of the interior of a metal mold is not possible. Therefore, air bubbles, or the like, which get trapped inside the mold and embedded in the casted part are undetected until the cured part is removed from the mold, at which time it is too late to correct and the cured part is scrap. High scrap rate further increases the cost of the associated composite part.
Therefore, there remains a need in the art of molding castable composite parts for methods of manufacturing molds and molds made thereby which are applicable to producing replicas of, as few as, a single part which incorporates high surface definition and intricate three dimensional detail in a timely manner. Additionally, there remains a need in the art for a method of making a mold that is transparent and that deforms to automatically eject the cured part from within the mold.